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The rem and millirem are CGS units in widest use among the U.S. public, industry, and government. [4] However, the SI unit the sievert (Sv) is the normal unit outside the United States, and is increasingly encountered within the US in academic, scientific, and engineering environments, and have now virtually replaced the rem. [5]
Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning.Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv.
The SI unit of measure for equivalent dose is the sievert, defined as one Joule per kg. [11] In the United States the roentgen equivalent man (rem), equal to 0.01 sievert, is still in common use, although regulatory and advisory bodies are encouraging transition to sievert. [12]
The roentgen or röntgen (/ ˈ r ɛ n t ɡ ə n,-dʒ ə n, ˈ r ʌ n t-/; [2] symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays, and is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air (statcoulomb per kilogram).
The sievert is named after Rolf Maximilian Sievert. As with every SI unit named for a person, its symbol starts with an upper case letter (Sv), but when written in full, it follows the rules for capitalisation of a common noun; i.e., sievert becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case.
The conversion calculation is dependent on the radiation energy levels, the type of radiation being detected and the radiometric characteristic of the detector. [ 1 ] The continuous current ion chamber instrument can easily measure dose but cannot measure counts.
In diagnostic radiology, the F-factor is the conversion factor between exposure to ionizing radiation and the absorbed dose from that radiation. In other words, it converts between the amount of ionization in air (roentgens or, in SI units, coulombs per kilogram of absorber material) and the absorbed dose in air (rads or grays).
That model calculates an effective radiation dose, measured in units of rem, which is more representative of the stochastic risk than the absorbed dose in rad. In most power plant scenarios, where the radiation environment is dominated by X- or gamma rays applied uniformly to the whole body, 1 rad of absorbed dose gives 1 rem of effective dose ...